Chimps Learn By Watching Others -- Just Like Humans

Aug. 24, 2005

Researchers have demonstrated that chimpanzees, those clever apes that are so much like us, pass their "culture" on to other members of their communities, just like humans. And, just like humans, once they've learned how to do something they tend to stick with it, even if it's not the best way to get the job done.

The need to conform, even among chimps, is very powerful.

For many years animal behaviorists have theorized that chimps pass their way of life on down the line through something called "cultural transmission," but they haven't been able to prove it.

Now, according to scientists at Emory University's Yerkes Research Center, and the University of St. Andrews, Scotland, they've been able to repeat in the laboratory what many experts suspect happens naturally in the wild.

And it's not just a matter of "monkey see, monkey do." Once they learn how to do something, they stick with it, apparently because the need to conform is as powerful in their communities as it is in ours.

Chimp Culture

"What's unique about chimpanzees is the fact that they've got about 39 different cultural behaviors," says Victoria Horner, an animal behaviorist at St. Andrews, co-author of a study published in the online edition of Nature. "It's a whole suite of different things that is unmatched by any other animal apart from us."

There are many examples of animals that seem to learn from others in their community, even some bird species for whom flying at first seems a bit awkward, but that's a far cry from differences in chimp populations that seem to reflect a cultural way of doing things that passes on from one generation to the next.

"People have been doing observations of chimps in the wild for a long time, and it's always been thought that different populations have different types of behaviors," Horner says. "For example, chimps in West Africa use stones to crack nuts that are too hard to bite, and chimpanzees elsewhere in Africa don't do it, although they've got the same kind of stones, the same kind of nuts, and the same kind of need to eat nuts as a food source. They just don't do it.

"There's a lot of examples like that, but it's very hard to really put your finger on what's going on. We're assuming that these cultures are passed down from one chimpanzee to the next, the same way as human cultures are. You can't really show that in the wild because it would be logistically difficult."

A Unique Test

So Horner and her colleagues came up with a way to get at the problem in an experimental environment. She was joined in the research by Frans B. M. de Waal of the Living Links Center at Yerkes, and Andrew Whiten of St. Andrews.

They were aided in what they call their "unique" study by two older female chimps that have a lot of clout in their communities. Erica and Georgia were taught two different ways of getting their lunch by manipulating a gizmo that works a little like an old fashioned pinball machine.

The "apparatus," as Horner calls it, consists of a transparent box with a piece of food inside. But the chimps can't get at the food because there's a square block in front of it.

Erica was taught how to get the food by using a stick to lift the block so the food would roll out. Georgia was taught to poke the block with the stick, pushing it back so she could get the morsel.

Other chimps were divided into three groups. Some were teamed up with Erica, who lifted the block. Others went with Georgia, who poked the block. And others were left to figure it out for themselves.

Erica and Georgia weren't teaching the other chimps, Horner says. They were simply trying to get lunch while others watched. And it turned out that in each group the others not only watched, they learned precisely how to mimic their elder and get at the food. Each group of 17 chimps had only one failure, possibly because one loser ranked so low in community standings that he or she never got a chance to try it.

As for the chimps in the third group, deprived of a leader who knew the rules of the game, none of them succeeded.

The Power of 'Chimpy' Conformity

And at that point the experiment might have ended, except for a twist that came as a bit of a surprise to the researchers. It shows that conformity is a powerful force indeed, even among chimps.

It turns out that poking was a more natural way of getting the food than trying to lift the block. It's a bit more "chimpy," as Horner puts it.

In the wild, chimps use sticks to poke into ant colonies to get at the ants, and it's a pretty easy thing for them to do.

So it wasn't a surprise when some of the chimps that had learned how to lift the block to get the food soon learned an easier way. Poke it instead.

But here's the surprise. They didn't stick with it. Instead, after experimenting with poking, they returned to the method they had learned from their elder, even though it wasn't the "chimpy" thing to do.

The researchers think their experiments demonstrate two things. Chimpanzees do, indeed, develop distinct cultures that are very persistent, probably even transmittable to their offspring. And they want to fit in with the rest of their group, so they conform, even if they have figured out a better way to get the job done.

Doesn't that sound, well, so human?

Lee Dye's column appears weekly on ABCNEWS.com. A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.